Method, apparatus and system for processing very-high-speed random access

ABSTRACT

A method, an apparatus and a system process very-high-speed random access. The method includes: selecting a ZC sequence group according to a cell type and a first cyclic shift parameter Ncs, and setting N detection windows for each ZC sequence in the ZC sequence group, where N≥5; sending the cell type, a second Ncs, and the ZC sequence group to a UE; receiving a random access signal sent by the UE, and obtaining the random access sequence from the random access signal; performing correlation processing on the random access sequence with each ZC sequence in the ZC sequence group, detecting a valid peak value in the N detection windows of each ZC sequence, and determining an estimated value of an RTD according to the valid peak value, so that a UE in a very-high-speed scenario can normally access a network, thereby improving network access performance.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 15/601,703, filed May 22, 2017, which is a continuation of U.S. patent application Ser. No. 14/600,615, filed Jan. 20, 2015, now U.S. Pat. No. 9,674,872, which is a continuation of International Application No. PCT/CN2013/076974, filed on Jun. 8, 2013, which claims priority to Chinese Patent Application No. 201210278680.4, filed on Aug. 7, 2012, and all of the afore-mentioned patent applications are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to the field of mobile communications systems, and in particular, to a method, an apparatus and a system for processing very-high-speed random access.

BACKGROUND

In a Long Term Evolution (Long Term Evolution, LTE) system, a random access channel (Random Access Channel, RACH) is mainly used for initial access of a user equipment (User Equipment, UE) and does not carry any user data. A signal sent by a UE on an RACH is a preamble (Preamble) sequence, where the preamble sequence is a Zadoff-Chu sequence (Zadoff-Chu sequence, ZC sequence). In the prior art, a Preamble may include two parts which are a section of cyclic prefix (Cyclic Prefix, CP) with a length of T_(CP) and a section of access sequence (Sequence, SEQ) with a length of T_(SEQ). In addition, parameter settings of different formats of Preambles may be matched to different cell radii, as shown in Table 1:

TABLE 1 Preamble sequence Maximum cell radius format No. T_(CP) T_(SEQ) (km) 0 3168 · T_(s) 24576 · T_(s) Approximately 14.6 1 21024 · T_(s)  24576 · T_(s) Approximately 77.3 2 6240 · T_(s) 2 · 24576 · T_(s) Approximately 29.6 3 21024 · T_(s)  2 · 24576 · T_(s) Approximately 100 4  448 · T_(s)  4096 · T_(s) Approximately 1.4

where T_(s) is a basic time unit in an LTE protocol, and T_(s)=1/(15000×2048)s.

In the prior art, a 0-15 km/h low speed scenario is optimized by the LTE system, so that relatively high performance is still achieved in a 15-120 km/h high speed movement scenario, and connection can still be maintained in a 120-350 km/h high speed movement scenario. In an existing LTE protocol, two cell configurations, an unrestricted cell configuration and a restricted cell configuration, are supported, where an unrestricted cell is applied to a low frequency deviation scenario (for example, the frequency deviation is less than 600 Hz), and a restricted cell is applied to a high frequency deviation scenario (for example, the frequency deviation is greater than 600 Hz). With regard to a restricted cell, when a random access signal sent by a UE uses a ZC sequence (Zadoff-Chu Sequence) as a random access sequence, an evolved base station (evolved Node B, NodeB or eNB or e-NodeB) can ensure correct detection of a round trip delay (Round Trip Delay, RTD) within a frequency deviation range

$\left\lbrack {{- \frac{3*\Delta \; f_{RA}}{2}},\frac{3*\Delta \; f_{RA}}{2}} \right\rbrack,$

where Δf_(RA) represents a subcarrier spacing of the random access channel, and the UE adjusts a timing advance (Timing Advance, TA) according to the RTD, thereby adjusting message sending timing and ensuring that the UE can normally access a network.

With the development of communications technologies and increased communications requirements of users, operators come up with requirements for coverage in very-high-speed movement scenarios and high frequency band high-speed railway scenarios. In the two types of scenarios, a frequency deviation of the random access signal is larger, which is

$\left\lbrack {{- \frac{W*\Delta \; f_{RA}}{2}},\frac{W*\Delta \; f_{RA}}{2}} \right\rbrack,$

where W≥5. It is very difficult for an eNB to ensure correctness of RTD detection under a high frequency deviation. As a result, it is very difficult to ensure that a UE normally accesses a network, which affects access performance of the network.

SUMMARY

Embodiments of the present invention provide a method, an apparatus and a system for processing very-high-speed random access, so that a user equipment in a very-high-speed movement scenario can normally access a network, so as to improve access performance of the network.

One aspect of the present invention provides a method for processing very-high-speed random access, including: selecting a ZC sequence group according to a cell type and a first cyclic shift parameter Ncs, and setting N detection windows for each ZC sequence in the ZC sequence group, where N≥5; sending the cell type, a second Ncs, and the ZC sequence group to a user equipment UE, so that the UE selects a random access sequence from the ZC sequence group; receiving a random access signal sent by the UE, and obtaining the random access sequence from the random access signal; and performing correlation processing on the random access sequence with each ZC sequence in the ZC sequence group, detecting a valid peak value in the N detection windows of each ZC sequence, and determining an estimated value of a round trip delay RTD according to the valid peak value.

Another aspect of the present invention provides an apparatus for processing very-high-speed random access, including: a selecting unit, configured to select a ZC sequence group according to a cell type and a first cyclic shift parameter Ncs; a setting unit, configured to set N detection windows for each ZC sequence in the ZC sequence group selected by the selecting unit, where N≥5; a sending unit, configured to send the cell type, a second Ncs, and the ZC sequence group selected by the selecting unit to a user equipment UE, so that the UE selects a random access sequence from the ZC sequence group; a receiving unit, configured to receive a random access signal sent by the UE and obtain the random access sequence from the random access signal; and a detecting unit, configured to perform correlation processing on the random access sequence obtained by the receiving unit with each ZC sequence in the ZC sequence group, detect a valid peak value in the N detection windows set by the setting unit for each ZC sequence, and determine an estimated value of a round trip delay RTD according to the valid peak value.

It can be known from the above technical solutions that, by using the embodiments of the present invention, a ZC sequence group is selected according to a cell type and a first cyclic shift parameter Ncs, N detection windows are set for each ZC sequence in the ZC sequence group, where N≥5, and an estimated value of the RTD is determined according to a valid peak value detected in the N detection windows of each ZC sequence. In this way, a problem that an RTD of a random access signal cannot be correctly detected in a very-high-speed scenario is solved, it is ensured that a user equipment moving at a very high speed can correctly adjust a TA value according to a detected RTD, and therefore message sending timing is correctly adjusted, so that the user equipment in a very-high-speed scenario can normally access a network, thereby improving access performance of the network.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings required for describing the embodiments. Apparently, the accompanying drawings in the following description show some embodiments of the present invention, and persons of ordinary skill in the art may still derive other drawings from these accompanying drawings without creative efforts.

FIG. 1 is a flowchart of a method for processing very-high-speed random access according to an embodiment of the present invention;

FIG. 2 is a flowchart of another method for processing very-high-speed random access according to an embodiment of the present invention;

FIG. 3 is a schematic diagram illustrating changing of a valid peak value with frequency deviations in detection windows according to an embodiment of the present invention;

FIG. 4 is a flowchart of another method for processing very-high-speed random access according to an embodiment of the present invention;

FIG. 5 is a flowchart of still another method for processing very-high-speed random access according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of a position relation between a valid peak value and an overlap between detection windows according to an embodiment of the present invention; and

FIG. 7 is a schematic structural diagram of an apparatus for processing very-high-speed random access according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The following clearly describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are merely a part rather than all of the embodiments of the present invention. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

As shown in FIG. 1, a method for processing very-high-speed random access according to an embodiment of the present invention is specifically described as follows:

101. Select a ZC sequence group according to a cell type and a first cyclic shift (cyclic shift) parameter Ncs, and set N detection windows for each ZC sequence in the ZC sequence group, where N≥5.

The cell type includes an unrestricted cell and a restricted cell, and may be configured according to an application scenario. For example, the cell type may be configured to unrestricted cell for a low speed scenario, and configured to restricted cell for a high speed scenario.

The first Ncs is used to represent a cell coverage range, that is, a cell coverage radius. The larger the first Ncs is, the larger the cell coverage range is. Configuration of the first Ncs belongs to the prior art, and therefore is not described herein any further.

The ZC sequence group includes M ZC root sequences, where M<64. In the 3GPP TS 36.211 protocol, 838 ZC root sequences are defined totally. The ZC sequence group may include 64 ZC root sequences at most.

The setting N detection windows for each ZC sequence in the ZC sequence group may specifically include the following steps.

The du_(HT) value of the i^(th) ZC sequence refers to a shift of a mirror image peak in a power delay profile PDP of the i^(th) ZC sequence relative to an RTD when a frequency deviation is

${\pm \frac{1}{T_{SEQ}}},$

where T_(SEQ) is a time duration occupied by the i^(th) ZC sequence and a value of i is any integer in [1, M].

The du_(HT) values may be obtained by using a manner A1 or a manner A2.

In the manner A1, the value is obtained by calculation according to Formula 1, which is detailed as follows:

$\begin{matrix} {{du}_{HT} = \left\{ \begin{matrix} {- p} & {0 \leq p < {N_{ZC}/2}} \\ {N_{ZC} - p} & {else} \end{matrix} \right.} & \left( {{Formula}\mspace{14mu} 1} \right) \end{matrix}$

where p is a minimum non-negative integer when (p·u) mod N_(zc)=1, u is a physical root sequence number of the ZC sequence, and Nzc is a length of the ZC sequence, where the Nzc may be 839 or 139. When Nzc is a fixed value, P is decided by a value of u. Then, according to the above Formula 1, the du_(HT) is decided by the value of u.

For example, if Nzc=839, when the physical root sequence number u=3, (p·3)mod 839=1, p=280, and du_(HT)=−280 can be obtained according to Formula 1; when the physical root sequence number u=836, (p·836)mod 839=1, p=1119, and du_(HT)=280 can be obtained according to Formula 1.

In the manner A2, the value is obtained by querying Table 2 or Table 3.

Table 2 lists du_(HT)(u) values when Nzc=839, where u=1, . . . , 419. When u=42Q, . . . , 838, du_(HT)(u) values can be obtained using a formula du_(HT)(Nzc−u)=−du_(HT)(u), u=1, . . . , 419. For example, when the physical root sequence number u=3, it can be obtained by querying the table that du_(HT)=−280; when u=450, Nzc−u=839−450=389. Let u′=389, and then du_(HT)(Nzc−u′)=−du_(HT)(u′)=−du_(HT)(389)=110.

TABLE 2 Values of du_(HT) when N_(ZC) = 839 u du_(HT) 1 −1 2 419 3 −280 4 −210 5 −168 6 −140 7 −120 8 −105 9 −373 10 −84 11 305 12 −70 13 129 14 −60 15 −56 16 367 17 148 18 233 19 −265 20 −42 21 −40 22 −267 23 −73 24 −35 25 302 26 −355 27 −404 28 −30 29 405 30 −28 31 −406 32 −236 33 −178 34 74 35 −24 36 −303 37 68 38 287 39 43 40 −21 41 266 42 −20 43 39 44 286 45 261 46 383 47 357 48 402 49 −137 50 151 51 329 52 242 53 −95 54 −202 55 61 56 −15 57 −368 58 −217 59 −128 60 −14 61 55 62 −203 63 −293 64 −118 65 −142 66 −89 67 288 68 37 69 −304 70 −12 71 −130 72 268 73 −23 74 34 75 −179 76 −276 77 −316 78 −398 79 −308 80 409 81 145 82 133 83 374 84 −10 85 −306 86 −400 87 135 88 143 89 −66 90 −289 91 378 92 −228 93 −415 94 −241 95 −53 96 201 97 −173 98 351 99 −339 100 −344 101 −108 102 −255 103 −391 104 121 105 −8 106 372 107 345 108 −101 109 254 110 −389 111 −257 112 412 113 −297 114 −184 115 321 116 311 117 294 118 −64 119 141 120 −7 121 104 122 −392 123 −191 124 318 125 396 126 273 127 218 128 −59 129 13 130 −71 131 −269 132 375 133 82 134 144 135 87 136 −401 137 −49 138 −152 139 169 140 −6 141 119 142 −65 143 88 144 134 145 81 146 408 147 234 148 17 149 366 150 330 151 50 152 −138 153 −170 154 −158 155 −249 156 −199 157 171 158 −154 159 248 160 −215 161 −370 162 −347 163 175 164 −353 165 300 166 187 167 211 168 −5 169 139 170 −153 171 157 172 −200 173 −97 174 −352 175 163 176 −348 177 237 178 −33 179 −75 180 275 181 394 182 189 183 298 184 −114 185 −322 186 212 187 166 188 299 189 182 190 393 191 −123 192 −319 193 −313 194 333 195 −327 196 −244 197 362 198 250 199 −156 200 −172 201 96 202 −54 203 −62 204 292 205 221 206 224 207 −381 208 −359 209 281 210 −4 211 167 212 186 213 −323 214 −247 215 −160 216 369 217 −58 218 127 219 272 220 225 221 205 222 291 223 −380 224 206 225 220 226 271 227 −377 228 −92 229 414 230 −259 231 −385 232 −264 233 18 234 147 235 407 236 −32 237 177 238 −349 239 337 240 416 241 −94 242 52 243 328 244 −196 245 −363 246 324 247 −214 248 159 249 −155 250 198 251 361 252 −283 253 −388 254 109 255 −102 256 390 257 −111 258 −413 259 −230 260 384 261 45 262 285 263 386 264 −232 265 −19 266 41 267 −22 268 72 269 −131 270 −376 271 226 272 219 273 126 274 395 275 180 276 −76 277 315 278 −335 279 −418 280 −3 281 209 282 −360 283 −252 284 387 285 262 286 44 287 38 288 67 289 −90 290 −379 291 222 292 204 293 −63 294 117 295 310 296 −411 297 −113 298 183 299 188 300 165 301 −354 302 25 303 −36 304 −69 305 11 306 −85 307 399 308 −79 309 −410 310 295 311 116 312 320 313 −193 314 −334 315 277 316 −77 317 397 318 124 319 −192 320 312 321 115 322 −185 323 −213 324 246 325 −364 326 −332 327 −195 328 243 329 51 330 150 331 365 332 −326 333 194 334 −314 335 −278 336 417 337 239 338 −350 339 −99 340 343 341 −342 342 −341 343 340 344 −100 345 107 346 371 347 −162 348 −176 349 −238 350 −338 351 98 352 −174 353 −164 354 −301 355 −26 356 403 357 47 358 382 359 −208 360 −282 361 251 362 197 363 −245 364 −325 365 331 366 149 367 16 368 −57 369 216 370 −161 371 346 372 106 373 −9 374 83 375 132 376 −270 377 −227 378 91 379 −290 380 −223 381 −207 382 358 383 46 384 260 385 −231 386 263 387 284 388 −253 389 −110 390 256 391 −103 392 −122 393 190 394 181 395 274 396 125 397 317 398 −78 399 307 400 −86 401 −136 402 48 403 356 404 −27 405 29 406 −31 407 235 408 146 409 80 410 −309 411 −296 412 112 413 −258 414 229 415 −93 416 240 417 336 418 −279 419 2

Table 3 lists du_(HT)(u) values when Nzc=139, where u=1, . . . , 69 When u=70, . . . , 138, du_(HT)(u) values can be obtained using a formula du_(HT)(Nzc−u)=−du_(HT)(u), u=1, . . . , 69.

TABLE 3 Values of du_(HT) when N_(ZC) = 139 u du_(HT) 1 −1 2 69 3 46 4 −35 5 −28 6 23 7 −20 8 52 9 −31 10 −14 11 −38 12 −58 13 32 14 −10 15 37 16 26 17 49 18 54 19 −22 20 −7 21 −53 22 −19 23 6 24 −29 25 50 26 16 27 36 28 −5 29 −24 30 −51 31 −9 32 13 33 −59 34 −45 35 −4 36 27 37 15 38 −11 39 57 40 66 41 61 42 43 43 42 44 60 45 −34 46 3 47 68 48 55 49 17 50 25 51 −30 52 8 53 −21 54 18 55 48 56 67 57 39 58 −12 59 −33 60 44 61 41 62 65 63 −64 64 −63 65 62 66 40 67 56 68 47 69 2

Then, determine start positions of the N detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th) ZC sequence.

The number N of detection windows may be preset inside a base station according to a frequency deviation range, or may be dynamically configured to the base station on an operation and maintenance console.

For example, as an embodiment, when the frequency deviation range is

$\left\lbrack {{- \frac{5*\Delta \; f_{RA}}{2}},\frac{5*\Delta \; f_{RA}}{2}} \right\rbrack,$

the number of detection windows of the ZC sequence may be configured to five, and, however, the number of detection windows of the ZC sequence may also be configured to more than five. When the frequency deviation range is

$\left\lbrack {{- \frac{W*\Delta \; f_{RA}}{2}},\frac{W*\Delta \; f_{RA}}{2}} \right\rbrack,$

and W>5, the number N of detection windows of the ZC sequence may be configured to W, and the number N of detection windows of the ZC sequence may also be configured to more than W.

Finally, set the N detection windows of the i^(th) ZC sequence according to start positions of the N detection windows of the i^(th) ZC sequence and a preset size of a detection window.

The size of a detection window may be preset according to the cell radius, and the window size is no less than an RTD corresponding to the cell radius. For example, based on the RTD corresponding to the cell radius, the detection window may be expanded according to a multipath delay.

102. Send the cell type, a second Ncs, and the ZC sequence group to a user equipment UE, so that the UE selects a random access sequence from the ZC sequence group.

The second Ncs refers to an index value that can ensure that the UE uses the ZC root sequence in the ZC sequence group as a random access sequence. For example, two configuration manners in the following may be used.

Manner 1: When the cell type is configured to unrestricted cell (or low-speed cell), the second Ncs index is 0.

Manner 2: When the cell type is configured to restricted cell (or high-speed cell), the second Ncs index is 14.

In manner 2, the second Ncs index is not limited to 14, and may be any other index that enables the UE to use a ZC sequence which does not shift cyclically as the random access sequence, so as to reduce an overlap probability of the N detection windows of the ZC sequence. The second Ncs may be set inside the base station, or determined according to the configured cell type inside the base station, or obtained by querying a table, and is sent to the UE in a system message.

It should be noted that the first Ncs in step 101 is set according to the cell coverage range, and reflects the cell coverage radius. The second Ncs in step 102 is only used to be sent to the UE, so that the UE uses the ZC root sequence in the ZC sequence group as the random access sequence rather than uses a ZC sequence that shifts cyclically as the random access sequence, which can reduce the overlap probability of the N detection windows. If the index value of the first Ncs in step 101 meets a condition of enabling the UE to use the ZC sequence which does not shift cyclically as the random access sequence, the first Ncs and the second Ncs may be the same.

Partial ZC sequences in the ZC sequence group are used for contention access, and partial ZC sequences are used for contention-free access. For contention access, the UE randomly selects one ZC sequence from ZC sequences used for contention access in the ZC sequence group as the random access sequence. For contention-free access, the base station indicates to the UE which ZC sequence in the ZC sequence group is to be used as the random access sequence.

103. Receive a random access signal sent by the UE, and obtain the random access sequence from the random access signal.

104. Perform correlation processing (correlation) on the random access sequence with each ZC sequence in the ZC sequence group, detect a valid peak value in the N detection windows of each ZC sequence, and determine an estimated value of a round trip delay RTD according to the valid peak value.

The valid peak value is obtained by determining a maximum peak value in each detection window and a position of the maximum peak value in each detection window, and is specifically described as follows:

When only one maximum peak value is greater than a detection threshold, the peak value greater than the detection threshold is selected as the valid peak value. The valid peak value may also be called a primary peak value.

When two or more than two maximum peak values are greater than the detection threshold, whether absolute positions of the two maximum peak values overlap is determined. If the absolute positions do not overlap, the two maximum peak values are selected as valid peak values, where a greater valid peak value in the two valid peak values is called a primary peak value and a smaller valid peak value in the two valid peak values is called a secondary peak value. If the absolute positions overlap, the two maximum peak values are the same peak value and used as the primary peak value, and a maximum peak value greater than the detection threshold detected in a detection window corresponding to a spacing of the frequency deviation of the detection window in which the primary peak value is located plus 1 or the frequency deviation minus 1 RACH subcarriers is a secondary peak value.

The detection threshold may be set according to a false-alarm performance requirement under discontinuous transmission.

The estimated value of the RTD is a deviation of the valid peak value relative to a start position of a detection window in which the valid peak value is located. If the start position of the detection window in which the valid peak value is located is shifted based on the start position determined according to the du_(HT) value of the ZC sequence, the estimated value of the RTD may be obtained according to a deviation value of the valid peak value relative to the start position of the detection window in which the valid peak value is located, a shift direction and shift sampling points, which is specifically described as follows:

Assuming that the start position of the detection window in which the valid peak value is located shifts left by preset sampling points, the estimated value of the RTD is a deviation value of the valid peak value relative to the start position of the detection window in which the valid peak value is located minus the number of the preset sampling points. Assuming that the start position of the detection window in which the valid peak value is located shifts right by the preset sampling points, the estimated value of the RTD is a deviation value of the valid peak value relative to the start position of the detection window in which the valid peak value is located plus the number of the preset sampling points.

By using the method for processing very-high-speed random access provided by the foregoing embodiment, a problem that an RTD of a random access signal cannot be correctly detected in a very-high-speed scenario is solved, it is ensured that a user equipment moving at a very high speed can correctly adjust a TA value according to a detected RTD, and therefore message sending timing is correctly adjusted, so that the user equipment in a very-high-speed scenario can normally access a network, thereby improving access performance of the network.

As shown in FIG. 2, a method for processing very-high-speed random access according to an embodiment of the present invention, where N detection windows are set for each ZC sequence in a ZC sequence group when a frequency deviation range of very-high-speed random access is

$\left\lbrack {{- \frac{5*\Delta \; f_{RA}}{2}},\frac{5*\Delta \; f_{RA}}{2}} \right\rbrack,$

where N=5, is specifically described as follows:

201. Select a ZC sequence group according to a cell type and a first Ncs.

For relevant descriptions of the cell type and the first Ncs as well as the ZC sequence group, refer to step 101.

The selecting a ZC sequence group according to a cell type and a first Ncs is specifically described as follows:

B1. Select the ZC sequence group according to the cell type and the first Ncs.

B2. Determine whether a du_(HT) value of each ZC sequence in the ZC sequence group meets a condition

${{du}_{HT}} \in {\left\lbrack {{Ncs}, \frac{{Nzc} - {Ncs}}{4}} \right\rbrack\bigcup{\quad{{\left\lbrack {\frac{{Nzc} + {Ncs}}{4},\frac{{Nzc} - {Ncs}}{3}} \right\rbrack\bigcup\left\lbrack {\frac{{Nzc} + {Ncs}}{3},\frac{{Nzc} - {Ncs}}{2}} \right\rbrack},}}}$

where Nzc is a length of each ZC sequence, and Ncs refers to the first Ncs;

if the du_(HT) value of at least one ZC sequence in the ZC sequence group does not meet the condition, return to step B 1; and

if du_(HT) values of the ZC sequences in the ZC sequence group all meet the condition, send the ZC sequence group to a user equipment;

where, for an obtaining manner of the du_(HT) value, reference may be made to relevant descriptions in step 101.

It should be noted that, when the du_(HT) value of each ZC sequence in the selected ZC sequence group meets the condition

${{du}_{HT}} \in {\left\lbrack {{Ncs},\frac{{Nzc} - {Ncs}}{4}} \right\rbrack\bigcup{\quad{{\left\lbrack {\frac{{Nzc} + {Ncs}}{4},\frac{{Nzc} - {Ncs}}{3}} \right\rbrack\bigcup\left\lbrack {\frac{{Nzc} + {Ncs}}{3},\frac{{Nzc} - {Ncs}}{2}} \right\rbrack},}}}$

the five detection windows set according to the du_(HT) value of each ZC sequence do not overlap, which improves correctness of RTD estimation.

For example, assuming that the cell type is restricted cell, the first Ncs set according to a cell radius is 15, the selected ZC sequence group includes 64 ZC sequences, and a length of a ZC sequence is 839, a method for selecting the ZC sequence group according to the cell type and the first Ncs is described with an example as follows:

First, select logical root sequence numbers of the 64 ZC sequences according to the cell type and the first Ncs.

Table 4 is a mapping table between Ncs values and logical root sequence numbers of a restricted cell. The first column includes two Ncs values of 15, where a first logical root sequence number corresponding to the first Ncs of 15 is 24, and a second logical root sequence number corresponding to the second Ncs of 15 is 819. Therefore, available logical root sequence numbers are [24, 819] when the first Ncs is 15.

TABLE 4 Mapping table between Ncs values and logical root sequence numbers of a restricted cell N_(CS) value (restricted cell) Logical root sequence number —  0-23 15 24-29 18 30-35 22 36-41 26 42-51 32 52-63 38 64-75 46 76-89 55  90-115 68 116-135 82 136-167 100 168-203 128 204-263 158 264-327 202 328-383 237 384-455 237 456-513 202 514-561 158 562-629 128 630-659 100 660-707 82 708-729 68 730-751 55 752-765 46 766-777 38 778-789 32 790-795 26 796-803 22 804-809 18 810-815 15 816-819 — 820-837

Then, obtain the physical root sequence numbers of the 64 ZC sequences according to a mapping table between the logical root sequence numbers and the physical root sequence numbers.

Table 5 provides the mapping between partial logical root sequence numbers and partial physical root sequence numbers.

TABLE 5 Mapping table between logical root sequence numbers and physical root sequence numbers Logical root sequence number (Logical root sequence number) Physical root sequence number (Physical root sequence number ^(u))  0-23 129, 710, 140, 699, 120, 719, 210, 629, 168, 671, 84, 755, 105, 734, 93, 746, 70, 769, 60, 779 2, 837, 1, 838 24-29 56, 783, 112, 727, 148, 691 30-35 80, 759, 42, 797, 40, 799 36-41 35, 804, 73, 766, 146, 693 42-51 31, 808, 28, 811, 30, 809, 27, 812, 29, 810 52-63 24, 815, 48, 791, 68, 771, 74, 765, 178, 661, 136, 703 64-75 86, 753, 78, 761, 43, 796, 39, 800, 20, 819, 21, 818 76-89 95, 744, 202, 637, 190, 649, 181, 658, 137, 702, 125, 714, 151, 688  90-115 217, 622, 128, 711, 142, 697, 122, 717, 203, 636, 118, 721, 110, 729, 89, 750, 103, 736, 61, 778, 55, 784, 15, 824, 14, 825 116-135 12, 827, 23, 816, 34, 805, 37, 802, 46, 793, 207, 632, 179, 660, 145, 694, 130, 709, 223, 616 136-167 228, 611, 227, 612, 132, 707, 133, 706, 143, 696, 135, 704, 161, 678, 201, 638, 173, 666, 106, 733, 83, 756, 91, 748, 66, 773, 53, 786, 10, 829, 9, 830 168-203 7, 832, 8, 831, 16, 823, 47, 792, 64, 775, 57, 782, 104, 735, 101, 738, 108, 731, 208, 631, 184, 655, 197, 642, 191, 648, 121, 718, 141, 698, 149, 690, 216, 623, 218, 621 204-263 152, 687, 144, 695, 134, 705, 138, 701, 199, 640, 162, 677, 176, 663, 119, 720, 158, 681, 164, 675, 174, 665, 171, 668, 170, 669, 87, 752, 169, 670, 88, 751, 107, 732, 81, 758, 82, 757, 100, 739, 98, 741, 71, 768, 59, 780, 65, 774, 50, 789, 49, 790, 26, 813, 17, 822, 13, 826, 6, 833 264-327 5, 834, 33, 806, 51, 788, 75, 764, 99, 740, 96, 743, 97, 742, 166, 673, 172, 667, 175, 664, 187, 652, 163, 676, 185, 654, 200, 639, 114, 725, 189, 650, 115, 724, 194, 645, 195, 644, 192, 647, 182, 657, 157, 682, 156, 683, 211, 628, 154, 685, 123, 716, 139, 700, 212, 627, 153, 686, 213, 626, 215, 624, 150, 689 328-383 225, 614, 224, 615, 221, 618, 220, 619, 127, 712, 147, 692, 124, 715, 193, 646, 205, 634, 206, 633, 116, 723, 160, 679, 186, 653, 167, 672, 79, 760, 85, 754, 77, 762, 92, 747, 58, 781, 62, 777, 69, 770, 54, 785, 36, 803, 32, 807, 25, 814, 18, 821, 11, 828, 4, 835 384-455 3, 836, 19, 820, 22, 817, 41, 798, 38, 801, 44, 795, 52, 787, 45, 794, 63, 776, 67, 772, 72 767, 76, 763, 94, 745, 102, 737, 90, 749, 109, 730, 165, 674, 111, 728, 209, 630, 204, 635, 117, 722, 188, 651, 159, 680, 198, 641, 113, 726, 183, 656, 180, 659, 177, 662, 196, 643, 155, 684, 214, 625, 126, 713, 131, 708, 219, 620, 222, 617, 226, 613 456-513 230, 609, 232, 607, 262, 577, 252, 587, 418, 421, 416, 423, 413, 426, 411, 428, 376, 463, 395, 444, 283, 556, 285, 554, 379, 460, 390, 449, 363, 476, 384, 455, 388, 451, 386, 453, 361, 478, 387, 452, 360, 479, 310, 529, 354, 485, 328, 511, 315, 524, 337, 502, 349, 490, 335, 504, 324, 515 . . . . . .

If the selected logical root sequence number is 384, the physical root sequence numbers of the 64 ZC sequences may be obtained according to the mapping between the logical root sequence numbers and the physical root sequence numbers in Table 5 as follows: 3, 836, 19, 820, 22, 817, 41, 798, 38, 801, 44, 795, 52, 787, 45, 794, 63, 776, 67, 772, 72, 767, 76, 763, 94, 745, 102, 737, 90, 749, 109, 730, 165, 674, 111, 728, 209, 630, 204, 635, 117, 722, 188, 651, 159, 680, 198, 641, 113, 726, 183, 656, 180, 659, 177, 662, 196, 643, 155, 684, 214, 625, 126, 713.

Then, obtain du_(HT) values of the 64 ZC sequences.

According to relevant descriptions and obtaining method of du_(HT) in step 101, it may be obtained that: when the physical root sequence number u=3, du_(HT)=−280; when the physical root sequence number u=836, du_(HT)=280; and when the physical root sequence number u=19, du_(HT)=265, . . . .

Finally, determine whether the du_(HT) values of the selected 64 ZC sequences all meet a condition

${{du}_{HT}} \in {\left\lbrack {{Ncs},\frac{{Nzc} - {Ncs}}{4}} \right\rbrack\bigcup{\quad{\left\lbrack {\frac{{Nzc} + {Ncs}}{4},\frac{{Nzc} - {Ncs}}{3}} \right\rbrack\bigcup{\left\lbrack {\frac{{Nzc} + {Ncs}}{3},\frac{{Nzc} - {Ncs}}{2}} \right\rbrack.}}}}$

If the condition is not met, reselect the ZC sequence group.

|du_(HT)|∈[15,206]∪[213,274]∪[284,412] is worked out by calculating according to the first Ncs and Nzc. In the selected 64 ZC sequences, when the physical root sequence numbers are 3 and 836, the du_(HT) values do not meet the du_(HT) value condition. Therefore, reselect 64 ZC sequences according to the selecting step of the ZC sequence group.

Assuming that the physical root sequence numbers of the reselected 64 ZC sequences are 56, 783, 112, 727, 148, 691, 80, 759, 42, 797, 40, 799, 35, 804, 73, 766, 146, 693, 31, 808, 28, 811, 30, 809, 29, 810, 27, 812, 24, 815, 48, 791, 68, 771, 74, 765, 178, 661, 136, 703, 86, 753, 78, 761, 43, 796, 39, 800, 20, 819, 21, 818, 95, 744, 202, 637, 190, 649, 181, 658, 137, 702, 125, 714, obtain du_(HT) values and determine that the du_(HT) values of the reselected 64 ZC sequences meet the du_(HT) condition.

202. Set N detection windows for each ZC sequence in the ZC sequence group, where N=5.

When the ZC sequence group includes M ZC sequences, the setting N detection windows for each ZC sequence in the ZC sequence group, where N=5, is specifically described as follows:

C1. Obtain a du_(HT) value of an i^(th) ZC sequence in the ZC sequence group.

The du_(HT) value of the i^(th) ZC sequence refers to a shift of a mirror image peak in a power delay profile PDP of the i^(th) ZC sequence relative to the RTD when a frequency deviation is

${\pm \frac{1}{T_{SEQ}}},$

where T_(SEQ) is a time duration occupied by the i^(th) ZC sequence and a value of i is any integer in [1, M].

C2. Set five detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th) ZC sequence.

First, obtain start positions of the five detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th) ZC sequence.

The five detection windows of the i^(th) ZC sequence are a detection window {circle around (1)}, a detection window {circle around (2)}, a detection window {circle around (3)}, a detection window {circle around (4)} and a detection window {circle around (5)}, respectively. The five detection windows {circle around (1)}, {circle around (2)}, {circle around (3)}, {circle around (4)} and {circle around (5)} respectively correspond to frequency deviations 0, −Δf_(RA), +Δf_(RA), −2Δf_(RA) and +2f_(RA). The details are as follows:

a start position of the detection window {circle around (1)} is 0;

a start position of the detection window {circle around (2)} is mod(du_(HT), Nzc);

a start position of the detection window {circle around (3)} is mod(−du_(HT), Nzc);

a start position of the detection window {circle around (4)} is mod(2*HT, Nzc); and

a start position of the detection window {circle around (5)} is mod(−2*du_(HT), Nzc);

where mod(du_(HT), Nzc) means du_(HT) mod Nzc, Nzc is a length of the i^(th) ZC sequence, and for an obtaining manner of the du_(HT) value, reference may be made to step 101.

Then, set the five detection windows of the i^(th) ZC sequence according to the start positions of the five detection windows and a preset size of a detection window.

The size of the detection window is consistent with relevant descriptions in step 101. The start position of the detection window may be shifted according to preset sampling points, so as to adapt to earlier or later transmission of a random access signal by a UE.

203. Send the cell type, a second Ncs, and the ZC sequence group to a UE, so that the UE selects a random access sequence from the ZC sequence group.

For relevant descriptions of the second Ncs, refer to step 102.

204. Receive a random access signal sent by the UE, and obtain the random access sequence from the random access signal.

205. Perform correlation processing on the random access sequence with each ZC sequence in the ZC sequence group, detect a valid peak value in the five detection windows of each ZC sequence, and determine an estimated value of an RTD according to the valid peak value.

The valid peak value and the estimated value of the RTD are consistent with relevant descriptions in step 104.

The determining the RTD according to the valid peak value may be obtained by using two methods as follows:

Method (1): Directly obtain the estimated value of the RTD according to a deviation of a primary peak value relative to a start position of a primary peak value detection window.

Method (2): Select and merge data of at least two detection windows according to a preset principle to obtain a new valid peak value, and estimate the RTD.

In the method (2), according to the preset principle, detection windows at two sides of the primary peak value may be merged, or a detection window in which the primary peak value is located and a detection window in which a secondary peak value is located may be merged, or all the detection windows may be merged. Since the detection windows are merged, a detection threshold of the valid peak value is increased accordingly. Therefore, a new valid peak value may be obtained, and the RTD may be estimated according to the obtained new effective value.

206. Estimate a frequency deviation according to a detection window in which the valid peak value is located.

An estimated value of the frequency deviation is used for rectifying a deviation of an uplink signal of the UE and demodulating a Message 3 message sent by the UE. The Message 3 carries an identifier of the UE.

FIG. 3 is a schematic diagram illustrating changing of a valid peak value with frequency deviations in detection windows. The estimating a frequency deviation according to a detection window in which the valid peak value is located specifically includes three cases as follows:

Case 1: When two valid peak values exist, if a primary peak value is located in a detection window {circle around (1)} and a secondary peak value is located in a detection window {circle around (3)}, a frequency deviation of an uplink signal of a UE may be estimated to be a value within a range of 0 to −½f_(RA) according to the schematic diagram of the peak values in each window changing with the frequency deviation as shown in FIG. 3. If a maximum peak value is in the detection window {circle around (3)} and a second maximum peak value is in a detection window {circle around (5)}, the frequency deviation of the uplink signal of the UE is estimated to be a value within a range of Δf_(RA) to 3/2Δf_(RA); and so on.

Case 2: If two valid peak values exist and are close, where one is located in the detection window {circle around (1)} and the other is located in the detection window {circle around (3)}, the frequency deviation of the uplink signal of the UE is estimated to be about −½Δf_(RA); if two valid peak values exist and are close, where one is located in the detection window {circle around (3)} and the other is located in the detection window {circle around (5)}, the frequency deviation of the uplink signal of the UE is estimated to be about 3/2Δf_(RA); and so on.

Case 3: If one valid peak value exists and is located in the detection window {circle around (1)}, the frequency deviation of the uplink signal of the UE is estimated to be 0; if one valid peak value exists and is located in the detection window {circle around (2)}, the frequency deviation of the uplink signal of the UE is estimated to be −Δf_(RA); if one valid peak value exists and is located in the detection window {circle around (4)}, the frequency deviation of the uplink signal of the UE is estimated to be −2Δf_(RA); and so on.

It should be noted that step 205 is optional. To be specific, the frequency deviation is not estimated. Instead, a Message 3 is demodulated by grades according to a frequency deviation range. For example, when the frequency deviation range is [−3 KHz, 3 KHz], demodulation may be performed by six grades, where 1 KHz is a grade.

In the method for processing very-high-speed random access provided by the foregoing embodiment, a ZC sequence group is selected according to a cell type and a first Ncs, it is ensured that du_(HT) values of ZC sequences in the ZC sequence group meet a condition

${{du}_{HT}} \in {\left\lbrack {{Ncs},\frac{{Nzc} - {Ncs}}{4}} \right\rbrack\bigcup{\quad{{\left\lbrack {\frac{{Nzc} + {Ncs}}{4},\frac{{Nzc} - {Ncs}}{3}} \right\rbrack\bigcup\left\lbrack {\frac{{Nzc} + {Ncs}}{3},\frac{{Nzc} - {Ncs}}{2}} \right\rbrack},}}}$

N non-overlap detection windows are set for each ZC sequence in the ZC sequence group according to the du_(HT) value of each ZC sequence in the ZC sequence group, where N=5, the valid peak values in the non-overlap detection windows are detected, and a round trip delay is determined. In this way, not only a problem of access of a UE to a network in a very-high-speed scenario where the frequency deviation range is

$\left\lbrack {{- \frac{5*\Delta \; f_{RA}}{2}},\frac{5*\Delta \; f_{RA}}{2}} \right\rbrack$

is solved, but also correctness of an estimated value of the RTD is improved.

As shown in FIG. 4, a method for processing very-high-speed random access according to an embodiment of the present invention, where N detection windows are set for each ZC sequence in a ZC sequence group when a frequency deviation range of the very-high-speed random access is

$\left\lbrack {{- \frac{5*\Delta \; f_{RA}}{2}},\frac{5*\Delta \; f_{RA}}{2}} \right\rbrack,$

where N=5, is specifically described as follows:

401. Select a ZC sequence group according to a cell type and a first Ncs.

The cell type is a restricted cell, and the first Ncs represents a coverage range of the restricted cell.

Selection of the ZC sequence group may be obtained according to a selecting principle for root sequences of the restricted cell in the prior art, and therefore is not described herein any further.

402. Set N detection windows for each ZC sequence in the ZC sequence group, where N=5.

For relevant descriptions of the setting N detection windows for each ZC sequence in the ZC sequence group, reference may be made to step 202.

403. Send the cell type, a second Ncs, and the ZC sequence group to a UE, so that the UE selects a random access sequence from the ZC sequence group.

For relevant descriptions of the second Ncs, refer to step 102.

404. Receive a random access signal sent by the UE, and obtain the random access sequence from the random access signal.

405. Perform correlation processing on the random access sequence with each ZC sequence in the ZC sequence group, detect a primary peak value in the five detection windows of each ZC sequence, and determine a search window for a secondary peak value according to the primary peak value.

Search one maximum peak value in each of the five detection windows of each ZC sequence, and determine whether absolute positions of two maximum peak values in the five maximum peak values overlap. If the absolute positions do not overlap, select a greater maximum peak value of the two maximum peak values as the primary peak value. If the absolute positions overlap, select windows in which the two maximum peak values are located as windows in which the primary peak value is located. For example, when the primary peak value appears in an overlap between two detection windows, the primary peak value is detected separately in the two detection windows, that is, the same peak value is detected twice. Therefore, whether the peak values are the same peak value may be determined by determining whether the absolution positions of the two maximum peak values overlap.

TABLE 6 Search window for secondary peak value Window where the primary Search window for peak value is located secondary peak value {circle around (1)} {circle around (2)}{circle around (3)} {circle around (2)} {circle around (1)}{circle around (4)} {circle around (3)} {circle around (1)}{circle around (5)} {circle around (4)} {circle around (2)} {circle around (5)} {circle around (3)} {circle around (2)}{circle around (5)} {circle around (1)}{circle around (3)} {circle around (3)}{circle around (4)} {circle around (1)}{circle around (2)} {circle around (4)}{circle around (5)} {circle around (2)}{circle around (3)}

For example, assuming that the primary peak value appears in an overlap between a detection window {circle around (4)} and a detection window {circle around (5)}, it can be known by referring to Table 6 that search windows for the secondary peak value are a window {circle around (2)} and a window {circle around (3)}.

406. Detect a secondary peak value in the search window for the secondary peak value, and determine, according to a combination of the detection window in which the primary peak value is located and a detection window in which the secondary peak value is located, a frequency deviation estimation window combination and an RTD estimation window.

Detect a secondary peak value in the search window for the secondary peak value. To be specific, find one maximum peak value in the search window for each secondary peak value, compare the maximum peak values, and select a greatest one which is greater than a detection threshold as the secondary peak value.

Determine the frequency deviation estimation window combination and the RTD estimation window by querying Table 7 according to the window in which the secondary peak value is located and the window in which the primary peak value is located.

For example, assuming that the primary peak value appears in an overlap between the detection window {circle around (4)} and the detection window {circle around (5)}, it can be known by referring to Table 7 that the secondary peak value is searched in the window {circle around (2)} and the window {circle around (3)}. When the secondary peak value is found in the detection window {circle around (2)}, the combination of detection windows after two peak value searches is {circle around (2)}, {circle around (4)} and {circle around (5)}. It can be known by referring to Table 7 that the detection window {circle around (4)} is selected to estimate the RTD, and the detection windows {circle around (2)} and {circle around (4)} are selected to estimate the frequency deviation. When the secondary peak value is found in the detection window {circle around (3)}, a combination of detection windows after two peak value searches is {circle around (3)}, {circle around (4)} and {circle around (5)}. It can be known by referring to Table 7 that the detection window {circle around (5)} is selected to estimate the RTD, and the detection windows {circle around (3)} and {circle around (5)} are selected to estimate the frequency deviation.

TABLE 7 Frequency deviation estimation window combination and RTD estimation window Window combination Frequency deviation after two peak value estimation window searches combination RTD estimation window {circle around (1)} Invariant Single window itself {circle around (2)} {circle around (3)} {circle around (4)} {circle around (5)} {circle around (1)}{circle around (2)} Window in which the {circle around (1)}{circle around (3)} primary peak value is {circle around (2)}{circle around (4)} located {circle around (3)}{circle around (5)} {circle around (2)}{circle around (5)} fail — {circle around (3)}{circle around (4)} {circle around (2)}{circle around (3)}{circle around (4)} {circle around (2)}{circle around (3)}{circle around (5)} {circle around (2)}{circle around (3)}{circle around (4)}{circle around (5)} {circle around (4)}{circle around (5)} {circle around (1)}{circle around (2)}{circle around (5)} {circle around (1)}{circle around (2)} {circle around (2)} {circle around (1)}{circle around (3)}{circle around (4)} {circle around (1)}{circle around (3)} {circle around (3)} {circle around (2)}{circle around (4)}{circle around (5)} {circle around (2)}{circle around (4)} {circle around (4)} {circle around (3)}{circle around (4)}{circle around (5)} {circle around (3)}{circle around (5)} {circle around (5)}

It should be noted that, if the frequency deviation estimation window combination shows fail, no user is detected in the detection windows of the ZC sequence. Otherwise, the RTD is estimated according to a designated RTD estimation window.

407. Determine the estimated value of the RTD according to a position of the valid peak value in the RTD estimation window.

The estimated value of the RTD is a deviation of the valid peak value in the RTD estimation window relative to a start position of the RTD estimation window. If the start position of the RTD estimation window is obtained by shifting preset sampling points, the estimated value of the RTD is a deviation value of the valid peak value in the RTD estimation window relative to the start position of the RTD estimation window plus or minus the number of the preset sampling points. The details are as follows.

Assuming that the start position of the RTD estimation window shifts left by the preset sampling points, the estimated value of the RTD is the deviation value of the start position of the RTD estimation window minus the number of the preset sampling points. Assuming that the start position of the RTD estimation window shifts right by the preset sampling points, the estimated value of the RTD is the deviation value of the start position of the RTD estimation window plus the number of the preset sampling points.

408. Determine an estimated value of the frequency deviation according to the frequency deviation estimation window combination.

For how to determine the estimated value of the frequency deviation according to the frequency deviation estimation window combination, reference may be made to relevant descriptions in step 206.

The estimated value of the frequency deviation is used for rectifying a deviation of an uplink signal of the UE, thereby demodulating a Message 3.

It should be noted that step 408 is optional. To be specific, the frequency deviation may not be estimated. Instead, a Message 3 is demodulated by grades according to a frequency deviation range. For example, when the frequency deviation range is [−3 KHz, 3 KHz], demodulation may be performed by six grades, where 1 KHz is a grade.

In the method for processing very-high-speed random access provided by the foregoing embodiment, a principle of selecting the ZC sequence for the restricted cell in the prior art is used to select a ZC sequence group, the five detection windows is set for each ZC sequence in the ZC sequence group, the valid peak value in the five detection windows of each ZC sequence is detected, and an RTD estimation window is determined according to a combination of the detection window in which the primary peak value is located and the detection window in which the secondary peak value is located, so that the estimated value of the RTD is determined. In this way, a problem of detecting the RTD when the valid peak value appears in the overlap between detection windows is solved, and processing of the random access signal in a very-high-speed movement scenario when the frequency deviation range is

$\left\lbrack {{- \frac{5*\Delta \; f_{RA}}{2}},\frac{5*\Delta \; f_{RA}}{2}} \right\rbrack$

is implemented, thereby improving access performance of a network.

As shown in FIG. 5, a method for processing very-high-speed random access according to an embodiment of the present invention, where N (N≥W) detection windows are set for each ZC sequence in a ZC sequence group when a frequency deviation range of the very-high-speed random access is

$\left\lbrack {{- \frac{W*\Delta \; f_{RA}}{2}},\frac{W*\Delta \; f_{RA}}{2}} \right\rbrack,$

where W≥5, is specifically described as follows:

501. Select a ZC sequence group according to a cell type and a first Ncs.

Selection of the ZC sequence group is obtained according to a configuration principle for root sequences of a restricted cell, which belongs to the prior art, and therefore is not described herein any further.

For relevant descriptions of the cell type and the first Ncs, refer to step 101.

502. Set N detection windows for each ZC sequence in the ZC sequence group.

When the ZC sequence group includes M ZC sequences, the setting N detection windows for each ZC sequence in the ZC sequence group is specifically described as follows:

D1. Obtain a du_(HT) value of an i^(th) ZC sequence in the ZC sequence group.

For relevant descriptions of the du_(HT) value and an obtaining method, reference may be made to step 101, where a value of i is any integer in [1, M].

D2. Determine start positions of the N detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th) ZC sequence.

The N detection windows {circle around (1)}, {circle around (2)}, {circle around (3)}, {circle around (4)}, {circle around (5)}, {circle around (6)}, {circle around (7)} . . . of the i^(th) ZC sequence respectively correspond to frequency deviations _(0/)−Δf_(RA/)+Δf_(RA/)−2Δf_(RA/)+2Δf_(RA/)−3f_(RA/)+3Δf_(RA/), . . . . The start positions are as follows:

a start position of the detection window {circle around (1)} is 0;

a start position of the detection window {circle around (2)} is mod(du_(HT), Nzc);

a start position of the detection window {circle around (3)} is mod(−du_(HT), Nzc);

a start position of the detection window {circle around (4)} is mod(2*du_(HT), Nzc);

a start position of the detection window {circle around (5)} is mod(−2*du_(HT), Nzc);

a start position of the detection window {circle around (6)} is mod(3*du_(HT), Nzc);

a start position of the detection window {circle around (7)} is mod(−3*du_(HT), Nzc); and

others can be so deduced;

where mod(du_(HT), Nzc) means du_(HT) mod Nzc, and Nzc is a length of the i^(th) ZC sequence.

D3. Set the N detection windows of the i^(th) ZC sequence according to the start positions of the N detection windows of the i^(th) ZC sequence and a preset size of a detection window.

The size of the detection window may be configured according to a cell radius, and is no less than an RTD corresponding to the cell radius.

503. Send the cell type, a second Ncs, and the ZC sequence group to a UE, so that the UE selects a random access sequence from the ZC sequence group.

For relevant descriptions of the second Ncs, refer to step 102.

504. Receive a random access signal sent by the UE, and obtain the random access sequence from the random access signal.

505. Perform correlation processing on the random access sequence with each ZC sequence in the ZC sequence group, detect a valid peak value in the N detection windows of each ZC sequence, and determine an estimated value of the RTD according to the valid peak value.

For relevant descriptions of the valid peak value, reference may be made to step 104.

The determining an estimated value of the RTD according to the valid peak value may include step E1 and step E2, which are specifically described as follows:

E1. Determine an RTD estimation window according to a detection window in which the valid peak value is located.

If the detection window of the ZC sequence in which the valid peak value is located does not overlap with other detection windows of the ZC sequence, randomly select one from the detection windows in which the valid peak value is located as the RTD estimation window; or,

if the detection window of the ZC sequence in which the valid peak value is located overlaps with other detection windows of the ZC sequence but at least one valid peak value appears in a non-overlap, determine a detection window in which the at least one valid peak value is located as the RTD estimation window; or,

if the detection window of the ZC sequence in which the valid peak value is located overlaps with other detection windows of the ZC sequence, and the valid peak value appears in the overlap, perform frequency deviation processing on the random access signal according to frequency deviations of two detection windows in which a primary peak value of the valid peak values is located to obtain a new valid peak value, and determine the frequency deviation and the RTD estimation window according to the new valid peak value.

Other detection windows of the ZC sequence refer to detection windows in the N detection windows of the ZC sequence except the detection window in which the valid peak value is located.

For example, assuming that N detection windows are set for each ZC sequence in step 503 and step 504, where N=6. To be specific, each ZC sequence has detection windows {circle around (1)}, {circle around (2)}, {circle around (3)}, {circle around (4)}, {circle around (5)}, and {circle around (6)}. If valid peak values are respectively detected in detection windows {circle around (3)} and {circle around (5)} of a first ZC sequence, determine whether detection windows {circle around (3)} and {circle around (5)} of the first ZC sequence overlap with other detection windows of the first ZC sequence, that is, detection windows {circle around (1)}, {circle around (2)}, {circle around (5)} and {circle around (6)} of the first ZC sequence.

That the detection windows overlap but at least one valid peak value appears in the non-overlap refers to that although the detection windows overlap, at least one valid peak value in the detected valid peak values appears in the non-overlap of the detection windows. At this moment, the detection window in which the valid peak value appearing in the non-overlap of the detection windows is located is selected to estimate the RTD. As shown in FIG. 6, it is described as follows by using five detection windows as an example.

As shown in FIG. 6(a), when a secondary peak value appears in a detection window {circle around (1)}, the detection window {circle around (1)} may be used to estimate an RTD.

As shown in FIG. 6(b), a primary peak value appears in an overlap between a detection window {circle around (2)} and a detection window {circle around (5)}, and no secondary peak value exists. New valid peak values are obtained after a frequency deviation of +1/−2f_(RA) is separately performed on a received signal, and frequency deviations are determined according to the new valid peak values, so as to determine an RTD estimation window.

As shown in FIG. 6(c), a primary peak value appears in an overlap between a detection window {circle around (3)} and a detection window {circle around (4)}, and a secondary peak value appears in an overlap between the detection window {circle around (2)} and the detection window {circle around (5)}. New valid peak values are obtained after a frequency deviation of −1.5/+1.5 Δf_(RA) is separately performed on the received signal, and frequency deviations are determined according to the new valid peak values, so as to determine the RTD estimation window.

As an embodiment, if the detection window of the ZC sequence in which the valid peak value is located overlaps with other detection windows of the ZC sequence and the valid peak value appears in the overlap, it is determined that no random access signal is detected in the detection window in which the valid peak value is located. Random access initiated by a UE fails, and access is initiated again.

E2. Determine the estimated value of the RTD according to a position of the valid peak value in the RTD estimation window.

For a specific implementation method of step C2, reference may be made to relevant descriptions in step 407.

It should be noted that the method for processing very-high-speed random access provided by the embodiment is applicable to a case in which a frequency deviation range is

$\left\lbrack {{- \frac{W*\Delta \; f_{RA}}{2}},\frac{W*\Delta \; f_{RA}}{2}} \right\rbrack$

and W≥5. When W>5, N detection windows are set for the ZC sequences in the selected ZC sequence group, where N is no less than W.

In the foregoing embodiment, a principle of selecting the ZC sequence for a restricted cell in the prior art is used to select the ZC sequence group, the N detection windows are set for each ZC sequence in the ZC sequence group, the valid peak value in the N detection windows of each ZC sequence is detected, and an RTD estimation window according to a detection window in which the valid peak value is located is determined, so that the round trip delay is determined. In this way, a problem that it is difficult to detect the RTD correctly in a very-high-speed scenario when a frequency deviation range is

$\left\lbrack {{- \frac{W*\Delta \; f_{{RA}\;}}{2}},\frac{W*\Delta \; f_{RA}}{2}} \right\rbrack$

and W≥5 is solved, thereby improving access performance of a network.

As shown in FIG. 7, an apparatus for processing very-high-speed random access according to an embodiment of the present invention may be a base station, which includes a selecting unit 701, a setting unit 702, a sending unit 703, a receiving unit 704, and a detecting unit 705.

The selecting unit 701 is configured to select a ZC sequence group according to a cell type and a first Ncs.

The setting unit 702 is configured to set N detection windows for each ZC sequence in the ZC sequence group, where N≥5.

The sending unit 703 is configured to send the cell type, a second Ncs, and the ZC sequence group selected by the selecting unit 701 to a user equipment UE, so that the UE selects a random access sequence from the ZC sequence group.

The receiving unit 704 is configured to receive a random access signal sent by the UE, and obtain the random access sequence from the random access signal.

The detecting unit 705 is configured to perform correlation processing on the random access sequence obtained by the receiving unit 704 with each ZC sequence in the ZC sequence group, detect a valid peak value in the N detection windows set by the setting unit 702 for each ZC sequence, and determine an estimated value of a round trip delay RTD according to the valid peak value.

Optionally, corresponding to the method embodiment shown in FIG. 1, when the ZC sequence group selected by the selecting unit 701 includes M ZC sequences, the setting unit 702 is further configured to:

obtain a du_(HT) value of an i^(th) ZC sequence in the ZC sequence group;

determine start positions of the N detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th) ZC sequence; and

set the N detection windows of the i^(th) ZC sequence according to the start positions of the N detection windows of the i^(th) ZC sequence and a preset size of a detection window.

The du_(HT) value of the i^(th) ZC sequence refers to a shift of a mirror image peak in a power delay profile PDP of the i^(th) ZC sequence relative to the RTD when a frequency deviation is

${\pm \frac{1}{T_{{SEQ}\;}}},$

where T_(SEQ) is a time duration occupied by the i^(th) ZC sequence and a value of i is any integer in [1, M]. For an obtaining method of the du_(HT) value, refer to relevant descriptions in step 101.

The size of a detection window may be configured according to a cell radius, and cannot be less than a maximum value of the RTD.

Optionally, when a frequency deviation range of the very-high-speed access is

$\left\lbrack {{- \frac{5*\Delta \; f_{RA}}{2}},\frac{5*\Delta \; f_{RA}}{2}} \right\rbrack$

and the ZC sequence selected by the selecting unit 701 includes M ZC sequences, that is, corresponding to the method embodiment shown in FIG. 2, the setting unit 702 is further configured to:

obtain a du_(HT) value of the i^(th) ZC sequence in the ZC sequence group; and

set five detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th) ZC sequence.

The du_(HT) value of the i^(th) ZC sequence refers to a shift of a mirror image peak in a power delay profile PDP of the i^(th) ZC sequence relative to the RTD when a frequency deviation is

${\pm \frac{1}{T_{{SEQ}\;}}},$

where T_(SEQ) is a time duration occupied by the i^(th) ZC sequence and a value of i is any integer in [1, M]. For an obtaining method of the du_(HT) value, refer to relevant descriptions in step 101.

Optionally, when the frequency deviation range of the very-high-speed random access is

$\left\lbrack {{- \frac{5*\Delta \; f_{RA}}{2}},\frac{5*\Delta \; f_{RA}}{2}} \right\rbrack$

and N detection windows are set for each ZC sequence in the ZC sequence group, where N=5, that is, corresponding to the method embodiment shown in FIG. 2, the setting unit 702 is further configured to:

obtain start positions of the five detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th) ZC sequence, where

a start position of a detection window {circle around (1)} is 0;

a start position of a detection window {circle around (2)} is mod(du_(HT), Nzc);

a start position of a detection window {circle around (3)} is mod(−du_(HT), Nzc);

a start position of a detection window {circle around (4)} is mod(2*du_(HT), Nzc);

a start position of a detection window {circle around (5)} is mod(−2*du_(HT), Nzc); and

set the five detection windows of the i^(th) ZC sequence according to the start positions of the five detection windows and a preset size of a detection window.

Nzc is a length of the i^(th) ZC sequence. For an obtaining method of the du_(HT) value, refer to relevant descriptions in step 101. For relevant descriptions of the preset size of the detection window, refer to step 104. The five detection windows {circle around (1)}, {circle around (2)}, {circle around (3)}, {circle around (4)} and {circle around (5)} respectively correspond to frequency deviations 0, −Δf_(RA), +Δf_(RA), −2Δf_(RA) and +2Δf_(RA).

Optionally, when the frequency deviation range of the very-high-speed random access is

$\left\lbrack {{- \frac{5*\Delta \; f_{RA}}{2}},\frac{5*\Delta \; f_{RA}}{2}} \right\rbrack,$

corresponding to the method embodiment shown in FIG. 2, the setting unit 701 is further configured to:

determine whether du_(HT) values of ZC sequences in the selected ZC sequence group meet a condition

${{du}_{HT}} \in {\left\lbrack {{Ncs},\frac{{Nzc} - {Ncs}}{4}} \right\rbrack\bigcup{\quad{{\left\lbrack {\frac{{Nzc} + {Ncs}}{4},\frac{{Nzc} - {Ncs}}{3}} \right\rbrack\bigcup\left\lbrack {\frac{{Nzc} + {Ncs}}{3},\frac{{Nzc} - {Ncs}}{2}} \right\rbrack},}}}$

where, in the condition, the Ncs is the first Ncs, and the Nzc is a length of a ZC sequence;

if the du_(HT) value of at least one ZC sequence in the selected ZC sequence group does not meet the condition, reselect a ZC sequence group according to the cell type and the first Ncs; and

if the du_(HT) values of the ZC sequences in the selected ZC sequence group all meet the condition, send the selected ZC sequence group to the setting unit 702 and the sending unit 703.

Optionally, corresponding to the method embodiment shown in FIG. 4, the detecting unit 704 is further configured to:

detect a primary peak value in the valid peak values in the five detection windows of each ZC sequence in the ZC sequence group;

determine a search window for a secondary peak value in the valid peak values according to a detection window in which the primary peak value is located;

detect the secondary peak value in the search window for the secondary peak value, and determine an RTD estimation window according to a combination relation between the detection window in which the primary peak value is located and a detection window in which the secondary peak value is located; and

determine the estimated value of the RTD according to a position of the valid peak value in the RTD estimation window.

Optionally, corresponding to the method embodiment shown in FIG. 5, the setting unit 702 is further configured to:

determine start positions of the N detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th) ZC sequence in the ZC sequence group as follows:

a start position of a detection window {circle around (1)} is 0;

a start position of a detection window {circle around (2)} is mod(du_(HT), Nzc);

a start position of a detection window {circle around (3)} is mod(−du_(HT), Nzc);

a start position of a detection window {circle around (4)} is mod(2*du_(HT), Nzc);

a start position of a detection window {circle around (5)} is mod(−2*du_(HT) Nzc);

a start position of the detection window {circle around (6)} is mod(3*du_(HT), Nzc).

a start position of a detection window {circle around (7)} is mod(−3*du_(HT), Nzc); and

others can be so deduced;

where mod(du_(HT), Nzc) means du_(HT) mod Nzc, and Nzc is a length of the i^(th) ZC sequence; and

set the N detection windows of the i^(th) ZC sequence according to the start positions of the N detection windows of the i^(th) ZC sequence and a preset size of a detection window.

The N detection windows {circle around (1)}, {circle around (2)}, {circle around (3)}, {circle around (4)}, {circle around (5)} . . . of the ZC sequence respectively correspond to frequency deviations 0, −Δf_(RA), +Δf_(RA), −2Δf_(RA), +2Δf_(RA), −3Δf_(RA) and +3Δf_(RA), . . . .

The detecting unit 704 is further configured to:

determine an RTD estimation window according to a detection window in which the valid peak value is located; and

if the detection window of the ZC sequence in which the valid peak value is located does not overlap with other detection windows of the ZC sequence, randomly select one from the detection windows in which the valid peak value is located as the RTD estimation window; or,

if the detection window of the ZC sequence in which the valid peak value is located overlaps with other detection windows of the ZC sequence, but at least one valid peak value appears in a non-overlap, determine a detection window in which the at least one valid peak value is located as the RTD estimation window; or

if the detection window of the ZC sequence in which the valid peak value is located overlaps with other detection windows of the ZC sequence, and the valid peak value appears in an overlap, determine that no random access signal is detected in the detection window in which the valid peak value is located; or perform frequency deviation processing on the random access signal according to frequency deviations of two detection windows in which a primary peak value of the valid peak values is located to obtain a new valid peak value, and determine the frequency deviation and the RTD estimation window according to the new valid peak value; and

determine the estimated value of the RTD according to a position of the valid peak value in the RTD estimation window.

Relevant descriptions of other detection windows in the ZC sequence are consistent with those in step 507.

Optionally, the detecting unit 704 is further configured to:

estimate the frequency deviation according to a detection window in which the valid peak value is located.

For the estimating the frequency deviation according to a detection window in which the valid peak value is located, refer to step 206.

It should be noted that the selecting unit 701, the setting unit 702, the sending unit 703, the receiving unit 704, and the detecting unit 705 may all be a CPU, a digital signal processor, or other processors.

The apparatus for processing very-high-speed random access provided by the foregoing embodiment solves a problem that an RTD of a random access signal cannot be correctly detected in a very-high-speed scenario, ensures that a user equipment moving at a very high speed can correctly adjust a TA value according to a detected RTD, and therefore correctly adjusts message sending timing, so that the user equipment in a very-high-speed scenario can normally access a network, thereby improving access performance of the network.

A system for processing very-high-speed random access provided by the embodiment includes the apparatus for processing very-high-speed random access shown in FIG. 7.

Persons of ordinary skill in the art may understand that all or a part of the steps of the foregoing method embodiments may be implemented by a program instructing relevant hardware. The program may be stored in a computer readable storage medium. When the program runs, the steps of the foregoing method embodiments are performed. The storage medium may include any medium capable of storing program code, such as a ROM, a RAM, a magnetic disk, or an optical disc.

Finally, it should be noted that the foregoing embodiments are merely intended for describing the technical solutions of the present invention rather than limiting the present invention. Although the present invention is described in detail with reference to the foregoing embodiments, persons of ordinary skill in the art should understand that they may still make modifications to the technical solutions described in the foregoing embodiments, or make equivalent replacements to some technical features thereof, as long as such modifications or replacements do not cause the essence of corresponding technical solutions to depart from the spirit and scope of the technical solutions of the embodiments of the present invention. 

What is claimed is:
 1. A method for processing very-high-speed random access, comprising: selecting, by a base station, a Zadoff-Chu (ZC) sequence group according to a cell type and a first cyclic shift parameter Ncs, wherein the ZC sequence group comprises M ZC sequences, and a du_(HT) value of a j^(th) ZC sequence in the ZC sequence group meets a condition ${{du}_{HT}} \in {\left\lbrack {{Ncs},\frac{{Nzc} - {Ncs}}{4}} \right\rbrack\bigcup{\quad{{\left\lbrack {\frac{{Nzc} + {Ncs}}{4},\frac{{Nzc} - {Ncs}}{3}} \right\rbrack\bigcup\left\lbrack {\frac{{Nzc} + {Ncs}}{3},\frac{{Nzc} - {Ncs}}{2}} \right\rbrack},}}}$ the Ncs in the condition is the first Ncs, the Nzc is the length of the j^(th) ZC sequence, and the value of j is 1, 2, 3, . . . , M; and sending, by the base station, the cell type, and the ZC sequence group to a user equipment (UE).
 2. The method according to claim 1, wherein the method further comprises: setting N detection windows for each ZC sequence in the ZC sequence group, wherein N≥5.
 3. The method according to claim 2, wherein the method further comprises: receiving a random access signal from the UE, and obtaining the random access sequence from the random access signal; and performing correlation processing on the random access sequence with each ZC sequence in the ZC sequence group, detecting a valid peak value in the N detection windows of each ZC sequence, and determining an estimated value of a round trip delay (RTD) according to the valid peak value.
 4. The method according to claim 3, wherein the setting N detection windows for each ZC sequence in the ZC sequence group comprises: obtaining a du_(HT) value of an i^(th) ZC sequence in the ZC sequence group; determining start positions of N detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th) ZC sequence; and setting the N detection windows of the i^(th) ZC sequence according to the start positions of the N detection windows of the i^(th) ZC sequence and a preset size of a detection window; wherein the du_(HT) value of the i^(th) ZC sequence corresponds to a shift of a mirror image peak in a power delay profile (PDP) of the i^(th) ZC sequence relative to the RTD when a frequency deviation is ${\pm \frac{1}{T_{{SEQ}\;}}},$ wherein T_(SEQ) is a time duration occupied by the i^(th) ZC sequence and a value of i is any integer in [1, M] . . . .
 5. The method according to claim 3, wherein, when a frequency deviation range of very-high-speed random access is $\left\lbrack {{- \frac{5*\Delta \; f_{RA}}{2}},\frac{5*\Delta \; f_{RA}}{2}} \right\rbrack$ in which Δf_(RA) represents a subcarrier spacing of a random access channel, the setting N detection windows for each ZC sequence in the ZC sequence group comprises: obtaining a du_(HT) value of an i^(th) ZC sequence in the ZC sequence group; and setting five detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th) ZC sequence; wherein the du_(HT) value of the i^(th) ZC sequence corresponds to a shift of a mirror image peak in a power delay profile (PDP) of the i^(th) ZC sequence relative to the RTD when a frequency deviation is ${\pm \frac{1}{T_{{SEQ}\;}}},$ wherein T_(SEQ) is a time duration occupied by the i^(th) ZC sequence and a value of i is any integer in [1, M].
 6. The method according to claim 5, wherein the setting five detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th) ZC sequence comprises: obtaining start positions of the five detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th) ZC sequence, wherein the five detection windows are a detection window {circle around (1)}, a detection window {circle around (2)}, a detection window {circle around (3)}, a detection window {circle around (4)} and a detection window {circle around (5)}, respectively; a start position of the detection window {circle around (1)} is 0; a start position of the detection window {circle around (2)} is mod(du_(HT), Nzc); a start position of the detection window {circle around (3)} is mod(−du_(HT), Nzc); a start position of the detection window {circle around (4)} is mod(2*du_(HT), Nzc); and a start position of the detection window {circle around (5)} is mod(−2*du_(HT), Nzc); wherein Nzc is a length of the i^(th) ZC sequence; and setting the five detection windows of the i^(th) ZC sequence according to the start positions of the five detection windows and a preset size of a detection window.
 7. The method according to claim 3, wherein the detecting a valid peak value in the N detection windows of each ZC sequence, and determining an estimated value of a round trip delay (RTD) according to the valid peak value comprises: detecting a primary peak value in the valid peak values in the N detection windows of each ZC sequence; determining a search window for a secondary peak value in the valid peak values according to a detection window in which the primary peak value is located; detecting the secondary peak value in the search window for the secondary peak value, and determining an RTD estimation window according to a combination relation between the detection window in which the primary peak value is located and a detection window in which the secondary peak value is located; and determining the estimated value of the RTD according to a position of the valid peak value in the RTD estimation window.
 8. The method according to claim 3, wherein the determining an estimated value of an RTD according to the valid peak value comprises: determining an RTD estimation window according to a detection window in which the valid peak value is located; and determining the estimated value of the RTD according to a position of the valid peak value in the RTD estimation window.
 9. The method according to claim 3, wherein the method further comprises: estimating the frequency deviation according to a detection window in which the valid peak value is located.
 10. The method according to claim 1, wherein the method further comprises: when the du_(HT) value of at least one ZC sequence in the ZC sequence group does not meet the condition, reselecting a ZC sequence group according to the cell type and the first Ncs.
 11. An apparatus for processing very-high-speed random access, comprising: a processor; and a computer readable storage medium to store instructions which, when executed by the processor, configure the processor to: select a Zadoff-Chu(ZC) sequence group according to a cell type and a first cyclic shift parameter Ncs, wherein the ZC sequence group comprises M ZC sequences, and a du_(HT) value of a j^(th) ZC sequence in the ZC sequence group meets a condition ${{du}_{HT}} \in {\left\lbrack {{Ncs},\frac{{Nzc} - {Ncs}}{4}} \right\rbrack\bigcup{\quad{{\left\lbrack {\frac{{Nzc} + {Ncs}}{4},\frac{{Nzc} - {Ncs}}{3}} \right\rbrack\bigcup\left\lbrack {\frac{{Nzc} + {Ncs}}{3},\frac{{Nzc} - {Ncs}}{2}} \right\rbrack},}}}$ the Ncs in the condition is the first Ncs, the Nzc is the length of the j^(th) ZC sequence, and the value of j is 1, 2, 3, . . . , M; and send the cell type, and the ZC sequence group to a user equipment (UE).
 12. The apparatus according to claim 11, wherein the processor is further configured to: set N detection windows for each ZC sequence in the ZC sequence group, wherein N≥5.
 13. The apparatus according to claim 12, wherein the processor is further configured to: receive a random access signal sent by the UE and obtain the random access sequence from the random access signal; and perform correlation processing on the random access sequence with each ZC sequence in the ZC sequence group, detect a valid peak value in the N detection windows for each ZC sequence, and determine an estimated value of a round trip delay (RTD) according to the valid peak value.
 14. The apparatus according to claim 13, wherein the processor is further configured to: obtain a du_(HT) value of an i^(th) ZC sequence in the ZC sequence group; determine start positions of N detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th) ZC sequence; and set the N detection windows of the i^(th) ZC sequence according to the start positions of the N detection windows of the i^(th) ZC sequence and a preset size of a detection window; wherein the du_(HT) value of the i^(th) ZC sequence corresponds to a shift of a mirror image peak in a power delay profile (PDP) of the i^(th) ZC sequence relative to the RTD when a frequency deviation is ${\pm \frac{1}{T_{{SEQ}\;}}},$ wherein T_(SEQ) is a time duration occupied by the i^(th) ZC sequence and a value of i is any integer in [1, M].
 15. The apparatus according to claim 13, wherein, when a frequency deviation range of very-high-speed random access is $\left\lbrack {{- \frac{5*\Delta \; f_{RA}}{2}},\frac{5*\Delta \; f_{RA}}{2}} \right\rbrack,$ the processor is further configured to: obtain a du_(HT) value of an i^(th) ZC sequence in the ZC sequence group; and set five detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th)ZC sequence; wherein the du_(HT) value of the i^(th) ZC sequence corresponds to a shift of a mirror image peak in a power delay profile (PDP) of the i^(th) ZC sequence relative to the RTD when a frequency deviation is ${\pm \frac{1}{T_{{SEQ}\;}}},$ wherein T_(SEQ) is a time duration occupied by the i^(th) ZC sequence and a value of i is any integer in [1, M].
 16. The apparatus according to claim 15, wherein the processor is further configured to: obtain start positions of the five detection windows of the i^(th) ZC sequence according to the du_(HT) value of the i^(th) ZC sequence, wherein the five detection windows are a detection window {circle around (1)}, a detection window {circle around (2)}, a detection window {circle around (3)}, a detection window {circle around (4)} and a detection window {circle around (5)}, respectively; a start position of the detection window {circle around (1)} is 0; a start position of the detection window {circle around (2)} is mod(du_(HT), Nzc); a start position of the detection window {circle around (3)} is mod(−du_(HT), Nzc); a start position of the detection window {circle around (4)} is mod(2*du_(HT), Nzc); and a start position of the detection window {circle around (5)} is mod(−2*du_(HT), Nzc); wherein Nzc is a length of the i^(th) ZC sequence; and set the five detection windows of the i^(th) ZC sequence according to the start positions of the five detection windows and a preset size of a detection window.
 17. The apparatus according to claim 11, wherein the processor is further configured to: when the du_(HT) value of at least one ZC sequence in the ZC sequence group does not meet the condition, reselect a ZC sequence group according to the cell type and the first Ncs.
 18. The apparatus according to claim 13, wherein the processor is further configured to: detect a primary peak value in the valid peak values in the N detection windows of each ZC sequence in the ZC sequence group; determine a search window for a secondary peak value in the valid peak values according to a detection window in which the primary peak value is located; detect the secondary peak value in the search window for the secondary peak value, and determine an RTD estimation window according to a combination relation between the detection window in which the primary peak value is located and a detection window in which the secondary peak value is located; and determine the estimated value of the RTD according to a position of the valid peak value in the RTD estimation window.
 19. The apparatus according to claim 13, wherein the processor is further configured to: determine an RTD estimation window according to a detection window in which the valid peak value is located; and when the detection window of the ZC sequence in which the valid peak value is located does not overlap with other detection windows of the ZC sequence, randomly select one from detection windows in which the valid peak value is located as the RTD estimation window; or when the detection window of the ZC sequence in which the valid peak value is located overlaps with other detection windows of the ZC sequence, but at least one valid peak value appears in a non-overlap, determine a detection window in which the at least one valid peak value is located as the RTD estimation window; or when the detection window of the ZC sequence in which the valid peak value is located overlaps with other detection windows of the ZC sequence, and the valid peak value appears in an overlap, determine that no random access signal is detected in the detection window in which the valid peak value is located; or perform frequency deviation processing on the random access signal according to frequency deviations of two detection windows in which a primary peak value of the valid peak value is located to obtain a new valid peak value, and determine the frequency deviation and the RTD estimation window according to the new valid peak value; and determine the estimated value of the RTD according to a position of the valid peak value in the RTD estimation window.
 20. The apparatus according to claim 13, wherein the processor is further configured to: estimate the frequency deviation according to a detection window in which the valid peak value is located. 